The Collaborative International Dictionary of English v.0.48:

Would-be \Would"-be`\, a.
   Desiring or professing to be; vainly pretending to be; as, a
   would-be poet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

would-be
    adj 1: unfulfilled or frustrated in realizing an ambition [syn:
           manque, would-be(a)]